There is proposed a sheet supplying apparatus externally attached to an image forming apparatus such as an MFP (Multi Function Peripheral). This sheet supplying apparatus is attached to the exterior of one side of the image forming apparatus. Several thousand sheets for printing are stacked on a tray provided for stacking the sheets. Therefore, the sheet supplying apparatus is also called LCF (LARGE-CAPACITY-FEEDER). The tray moves up as the number of stacked sheets decreases by a lift mechanism in the sheet supplying apparatus to keep the top position of the sheets stacked on the tray at certain height. The sheets stacked on the tray are picked up by a pickup roller one by one in order from the sheet at the top position, delivered to a separating and conveying roller pair configured to, for example, prevent double feeding of sheets, and fed to a sheet conveying system in the MFP.
In the sheet supplying apparatus, a sheet stacking section in which a tray capable of moving up and down is provided in a housing-like exterior member which is configured to be drawn out therefrom in a drawer like fashion. When the sheet stacking section is drawn out the tray appears.
When a user refills the sheet stacking section with sheets, in order to supply sheets, a user draws out the sheet stacking section and sequentially stacks up the sheet bundles on the tray.
In the sheet supplying apparatus, a driven portion of the lift up mechanism is engaged with a driving source of the sheet supplying apparatus when the sheet stacking section is fully attached in the housing-like exterior member, i.e., not drawn out. On the other hand, the engagement between the driven portion and the driving source is released when the sheet stacking section is drawn out from the housing-like exterior member.
However, when the sheet stacking section is drawn out from the housing-like exterior member while a large number of sheets are stacked on the tray, the tray with the large number of sheets suddenly falls or drops because of the disengagement between the driven portion and the driving source.
It is possible to use, for example, a centrifugal brake or a helical torsion spring having high torsional torque to prevent a tray with a large number of sheets from a collision against an end of the tray guide member (shock absorption).
However, the centrifugal brake and the helical torsion spring having high torsional torque are generally expensive.